The invention relates to a flexible circuit board that is assembled as an electronic part in portable apparatuses such as cameras, and is capable of shielding a circuit element from electromagnetic waves.
In a portable apparatus such as a camera, a flexible circuit board is used for assembling lots of electronic parts herein, and for connecting the electronic parts to each other. The flexible circuit board includes conductive wiring patterns formed on a flexible insulating sheet by photo etching or the like. Electronic devices, such as an IC, a photo sensor and so on, are placed at suitable positions on the flexible circuit board and are connected to each other. In general, the front and rear surfaces of the flexible circuit board are covered with insulating layers for preventing a wiring pattern from being conducted to other wiring pattern formed on other circuit board. If necessary, the flexible circuit board is folded inside the portable apparatus.
A camera for IX240 type has a magnetic head and an interface IC for recording magnetically to a photo film. In IX240 type photo film, a magnetic recording area is provided outside of each frame. In feeding the photo film after a photography, the interface IC sends signals including some information of the photography to the magnetic head, in which the information is recorded magnetically on the magnetic recording area of the photo film. This information includes a taking date, whether flash light is projected, and so on. This recorded information is read out in printing operation.
In addition, some cameras are able to use a halfway used photo film cartridge in which unexposed frames remain. When this cartridge is loaded in the camera, the photo film is fed from the cartridge. In feeding, information of a previous photography recorded in the recording area is read out by the magnetic head, and signals including the information is sent to the interface IC, so that the camera can detect exposed frames. When no information of a previous photography is read out, the camera stops feeding the photo film and is on standby for photography.
The camera has lots of circuit elements such as a main CPU for controlling sequence of a photography, a flash circuit, an auto focusing circuit, an LCD panel for displaying information, an LCD driver and switches that are turned on and off according to external operation. Some of them are placed on the flexible circuit board on which the magnetic head interface IC is placed.
In reproducing a signal sent from the magnetic head, a current can be flown through a wiring pattern nearby the interface IC for sending a signal that is indifferent to. The current generates an electromagnetic wave that interferes with the reproductive signal as noise. Thus, misreading of the information is likely to occur. Since peculiar frequency modulation is used in magnetic recording onto the recording area in the photo film, even a small signal of high frequency generated nearby the interface IC may cause misreading.
The present invention is to provide a flexible circuit substance for protecting a circuit element against noise generated by a current flown near the circuit element.
To achieve the above objects, a flexible circuit board of the present invention is comprised of an insulating sheet with flexibility which has a first surface and a second surface, a first portion provided in the insulating sheet, a first circuit element that is provided on the first surface of the first portion and connected to a part of the wiring patterns, a first shield pattern formed on the second surface of the first portion, and a second shield pattern formed on the remnant portion in association with the first shield pattern. The first portion is folded onto a remnant portion of the insulating sheet with the first surface inside, The first and second shield patterns guard a front and a rear surfaces of the first circuit element against electromagnetic waves. Thereby, it is possible to prevent a circuit element from being interfered with electromagnetic waves from a wiring pattern nearby the circuit element.
In the embodiment, the wiring patterns are formed on the second surface. A U-shaped first opening is formed around the first portion, which is folded such that a folded portion is formed along a line that connects both end of the first opening. The flexible circuit includes at least one second opening that is formed on the line, a second circuit element that is disposed outside the folded portion, and at least one terminal attached to the second circuit element. The terminal is connected to said first circuit element through said second opening.
The flexible circuit board is integrated into a camera for exposing a subject image onto a photo film. The second circuit element is a magnetic head for recording information of photography onto a magnetic recording layer and for reading information magnetically. The first circuit element is a magnetic head interface IC for reproducing signals that is read out by the magnetic head and for sending information of photography to the magnetic head.